1. Field of the Invention
The present invention relates to a novel method for manufacturing an a catalyst for co-producing 1,1,1,2-tetrafluoroethane (CF.sub.3 CH.sub.2 F, hereinafter refers to HFC-134a), pentafluoroethane(CF.sub.3 CHF.sub.2, herein after refers to HFC-125), and 1,1,1-trifluoroethane (CF.sub.3 CH.sub.3, hereinafter refers to HFC-143a) simultaneously, and also a process for co-producing HFC-134a, HFC-125, and HFC-143a by two-step gaseous phase reaction using the said catalyst. Specifically, the present invention relates to a method that characterized in that in the first step, 1,1,1-trifluoro-2-chloroethane(CF.sub.3 CH.sub.2 Cl, hereinafter HFC-133a) is reacted with hydrogenfluoride(HF) in the presence of catalyst which comprising iron, nickel, chromium and zinc compound, to obtain HFC-134a, HFC-125 and HFC-143a and then, at the second step, trichloroethylene(CCl.sub.2 CHCl, hereinafter TCE) is added to the said reaction product of the first step to obtain HCFC-133a and then, HFC-134a, HFC-125, and HFC-143a are separated and HCFC-133a is recycled to the first step reaction.
2. Description of the Prior Art
It has been revealed that CFC(Chlorofluorocarbon) widely used as coolant, cleaning agent, and blowing agent, is a primary factor of destroying the ozone layer in stratosphere. Therefore, its production and use has been restricted under the international agreement. As a result of testifying widely the toxicity, safety, and physical and chemical efficiency of the target material for a long time to develop a material which can be substituted for these CFC compounds, it has been known that compounds such as difluoromethane(HFC-32), trifluoromethane(HFC-23), 1,1-difluoroethane(HFC-152a), 1,1,1,2-tetrafluoroethane(HFC-134a), pentafluoroethane (HFC-125), 1,1,1-trifluoroethane and like are favorable CFC substitutes. Among these, HFC-134a has been studied for mass production as a prominent substitute for dichloromethane(CFC-12) which has been used as an essential coolant. But other materials have not been researched sufficiently for use and it is tried to use as a special coolant as mixed one another. For example, the research has been made for a mixture of HFC-134a, HFC-32 and HFC-143a, and a mixture of HFC-134a, HFC-32 and HFC-125 as low temperature coolant for practice.
The methods for producing HFC-134a are disclosed in EP No. 0 449 617 A2 and Korea Patent Laid-Open No. 91-16657 and so forth. In EP No. 0 449 617 A2, TCE and HF are used as starting materials and HFC-134a is manufactured by two step reaction method. In Korea Patent Laid-open No. 91-16657, it is disclosed that reaction temperature is easily controlled and the formation of 1,1-difluoro-2-chloroethylene(CF.sub.2 CHCl, HCFC-1122) is suppressed by feeding the inactive gases into reactor when HFC-134a is produced by two-step using TCE and HF as the starting materials.
According to U.S. Pat. No. 4,129,603, chromium hydroxide is treated under steam condition and then, converted to chromium oxyfluoride form by hydrogen fluoride and this is used for manufacturing HFC-134a. But this method has a default that HCFC-1122(CF.sub.2 CHCl), which is difficult to separate from HFC-134a, is produced in large amount as a by-product and a supplemental reactor is needed to remove thereof.
In DE Patent No. 29 32 934, chromium fluoride or chromium oxyfluoride is used as a catalyst. It shows a high selectivity about 98% around reaction temperature of 400.degree. C. but its activity is lowered after 44 hours. As oxygen is supplied continuously together with reactants, separation of HCl produced is difficult and the corrosion of apparatus is accelerated by moisture. Therefore this method is disadvantageous to be processed.
Several methods for producing HFC-125 are disclosed; methods that tetrachloroethylene(CCl.sub.2 CCl.sub.2) is reacted with HF on a catalyst comprising alumina and chromium as main components are disclosed in Japan Patent Laid-Open No. 90-178237 and U.S. Pat. No. 3,258,500; and a method that HCFC-122 (CF.sub.2 ClCHCl.sub.2) is fluorinated on a catalyst mainly consisting of alumina, in the presence of oxygen to obtain HCFC-123(CF.sub.3 CHCl.sub.2), HCFC-124(CF.sub.3 CHClF) and HFC-125(CF.sub.3 CHF.sub.2) is described in Japan Patent Laid-Open No. 92-29940. But these methods are not economic due to a low selectivity to HFC-125 and yielding a large amount of side product.
As a process for manufacturing HFC-143a, it is proposed in Japan Patent Publication No. 84-46211 and U.S. Pat. No. 4,091,043 that 1,1,1-trichloroethane(CCl.sub.3 CH.sub.3) is reacted with HF in the presence of SbCl.sub.5 to produce HCFC-142b and HFC-143a simultaneously. And it is also described that among the reaction products HFC-143a can be obtained up to about 80% by the method.